1. Field of the Invention
The present invention relates to propulsive wings and traction kites, used for applying a traction force and/or pulling a load. More particularly the present invention relates to a sport traction kite having a generally tubular inflatable leading edge that is concave when viewed from the side in flight mode.
2. Description of Related Art
The use of kites as a means of propulsion has existed for over a century. Kites were first used as a means of propulsion in pulling boats. The use of sport kites in water and land based activities, such as kiteboarding and snowboarding, has grown tremendously in recent years. These sports adapt the principals of surfing and snowboarding to include kites as a method for generating propulsion, speed, and elevation. A number of advances in kite design have led to improvements in safety, attainable speeds, and overall performance.
Most sport traction kites currently used in board sports are constructed with flexible canopy having an inflatable leading edge armature which distributes loads via ropes attached along the leading edge and at the lateral ends. As used therein the terms “sport kite,” “traction kite,” or “kite” shall mean a propulsive wing that harnesses wind power to pull a rider over or through, land, water, or snow on a riding platform (e.g. a board). A traction kite of this type is described in U.S. Pat. No. 4,708,078 to Legaignoux et al., wherein a basic design for a leading edge inflatable (“LEI”) kite is disclosed. Legaignoux discloses a traction kite having a leading edge with an inflatable leading edge armature covered by a flexible envelope.
As kite sports have evolved, demand for kites with improved performance characteristics has grown. Specifically, kite users desire kites with improved handling and control, faster turning speeds, and more responsive control achieved with minimal user input force. As a result, several different types of leading edge inflatable kites have been developed. The C-kite is the most common kite design that has been available for the longest period of time. It is named for the arc-like shape it forms while in flight which resembles the letter “C”. The attachment of four lines at the four corners of the kite cause the kite to arc sharply while in flight. When viewed from overhead, the C-kite characteristically forms a convexly shaped trailing edge. FIG. 1 depicts a side view of a prior art C-kite, generally referenced as 1, having an inflatable leading edge 2, a trailing edge 3, and a canopy 4, supported by inflatable struts or ribs 5. A slight variation of the C-kite is the 5th line C-kite which includes an extra line attached at the middle of the leading edge of the kite. The sole purpose of the 5th line is to assist the rider in de-powering and re-launching the kite. De-powering is essentially a safety mechanism for the rider which reduces the propulsive surface area thereby reducing the force of the wind on the kite and the lines.
A recent innovation in kite design was the introduction of the Bow kite. The Bow kite has two defining characteristics which differentiate it from the C-kite: 1) the trailing edge of the bow kite is concave; and 2) the Bow kite is controlled by a series of control lines, commonly referred to as a bridle. The bridle is affixed to the kite in a web-like fashion and causes the kite to possess a flatter shape when in flight. The concave trailing edge and the addition of the bridle to the leading edge of the kite allow the kite to be de-powered with ease thus eliminating the need for a 5th line. Furthermore, these features allow the bow kite to be adaptable to varying wind speeds, whereas the C-kite's design relegates it to specific wind speeds. U.S. Pat. No. 7,374,133, issued to Legaignoux et al., provides an example of a conventional Bow kite.
Even more recently hybrid kites have been produced which combine elements of both the C-kite and the Bow kite. Although there are various forms of hybrid kites, all of the known versions are characterized as having convex trailing edge and a leading edge bridle. The convex trailing edge is adapted from the C-kite and the leading edge bridle and bow configuration is adapted from the Bow kite. The hybrid kite achieves a middle ground between the C-kite and the Bow kite. It possesses a greater ability to de-power than the C-kite, but also allows for a greater performance and turning capability than the Bow kite.
In general there has been an increased demand for fraction kites having improved performance characteristics for use in kite sports, such as kiteboarding and snowkiting (a/k/a snow kiteboarding). The curvature of the vertical leading edge of the kite in flight affects the performance of the kite. The angle and radii of curvature from the bridle tie-lines to the top of the kite dictate the size of the surface area of the central propulsive region. The greater the surface area, the greater the performance of the kite.
As stated in the aforementioned background, the curvature of the various edges of the kite affects the performance characteristics that the kite will possess. The Bow kite handles a myriad of wind velocities and can be easily depowered due to a concave trailing edge. Likewise, the C-kite's convex trailing edge gives the rider a more direct feel when riding and provides greater responsiveness to rider maneuvers. Furthermore, it is well known that a convex leading edge is the most effective design for all supported leading edge kites.
One known prior art kite, sold by Globe Kites, under the designation V-SONIC, wherein a small projecting V-shape was formed at the mid-point of the leading edge. While providing a marginal increase in surface area, the V-SONIC kite failed to achieve significant performance enhancement since the wingtips were swept back as was customary on Bow and hybrid kites. As a result, the V-SONIC kite failed to realize gains and advantages in performance characteristics relating to fast and responsive turning as the V-SONIC kite leading edge, when viewed from the side, extends from the propulsive region to the tip in a liner shape and thus fails to maximize the surface area transition between the propulsive center region.
The prior art fails to disclose or suggest a propulsive wing in which the curvature of the vertical portion of the leading edge of the kite is concave when viewed from the side in flight mode. This curvature also lends itself greatly to the performance of the kite. There is therefore a need for a propulsive wing with an inflatable support structure that is designed to maximize the surface area of the central propulsive region, while still providing a responsive and easily-controllable kite.